We are certainly willing to replace the engine of your destroyer with a Nageraboshi engine type. but this is more difficult than when we refit a transport. The cruiser type engine will have to be custom fitted and it takes alot longer to intergrate it with the vessel's systems. Looking at the time and resources we have to put into this, we require a payment of 50 million credits.
As for your colleague Mister Juan Cortés. Since it takes no additional specialisation to install the engine on a transport and you are our allies, he is free to purchase one on our bases. If you can give us the name of his vessel, we will add it the database of approved technology use as a formality.